The present invention relates to a device for waterproofing around a terminal bolt, and particularly relates to a waterproofing device for preventing water from entering from around a terminal bolt projecting from the casing of a coaxial starter.
In a coaxial starter, an electromagnetic switch is provided at one end of a DC motor in such a manner that the actuator of the switch, the armature shaft of the motor and an output rotary shaft are disposed coaxially to each other, as disclosed in the Japanese Patent Application Examined Publication No. 52773/82. Since the electromagnetic switch is provided at one end of the dc motor, a terminal bolt for electrically connecting the battery of a vehicle to the plus brush of the motor through the fixed and movable contacts of the switch projects from the casing of the coaxial starter. In a conventional device for waterproofing the portion of the casing, through which the terminal bolt extends, a rubber grommet having a groove on the outside circumferential surface of the grommet is fitted in an opening of the casing so as to engage the edge of the casing around the opening thereof in the groove of the grommet, the terminal bolt is inserted through the center hole of the grommet, and a nut as a tightening member is screw-engaged with the terminal bolt so as to put the grommet in pressure contact with the casing around the opening thereof. However, since the nut directly presses the grommet onto the casing, the nut can be rotated to any extent as far as the grommet is deformed by the nut. For that reason, there is a problem that it is very difficult to properly set the degree of tightening of the nut onto the grommet. Besides, since the nut is in contact with the grommet but not with the casing, the nut is always in an insufficiently tightened state. For that reason, there is another problem, in that the nut and a lead wire for attaching a lead wire extending from the battery or the brush are very likely to loosen due to the intense vibration of the vehicle.